I’ve praised the successful shift from flood irrigation toward more efficient technology – meaning things like center-pivot and drip over flood irrigation – that has enabled a downward trend in the amount of water applied to a typical irrigated acre of farmland in the United States. According to the USGS, US farmers decreased their average annual application of water from 2.8 acre feet per acre in 1970 to 2.07 in 2010, the most recent year for which data are available.
That’s a good thing, right?
Not in all cases, as this piece by John O’Connell at Capital Press explains:
[F]lood irrigation, with its leaky canals and standing water, helps recharge shrinking aquifers and provides migratory birds with a stopover on their annual pilgrimages between the Arctic and points south.
Unlikely partnerships of agricultural landowners, conservationists, government officials and water managers are behind efforts to keep farmers flooding fields in Idaho, Oregon, Washington and California. During the past year, Colson estimates the movement has maintained flood irrigation on roughly 4,000 acres across the West.
“For 15 or 20 years or more, the conservation community has been telling people how wasteful flood irrigation is and convert to sprinkler,” Colson said.
Here’s an interesting bit on the recharge of shallow aquifers:
In December of 2015 irrigators hoping to improve their own water outlook partnered with Farm Bureau, local cities and counties, Friends of the Teton River, Teton County Soil and Water Conservation District, Water District 1, the Henry’s Fork Foundation and others to form the Teton Water Users Association.
The association is pursuing funds to rebuild flood-irrigation infrastructure, which irrigators will use to flood pastures within their existing water rights during peak spring flows. When flows subside, they’ll resume using only efficient sprinklers. The water they bank through canals and flood irrigation should emerge from springs about three months later, when it’s needed most, extending the irrigation season, cooling the river for native Yellowstone cutthroat trout and replenishing dried marshes.
The story is a fascinating throughout, an example of why we have to be careful about how we think about water that is being “wasted”. It’s always going somewhere and doing something.
one disadvantage of flood irrigation is the possibility of leaching nutriments past the crop’s root zone and into the aquifer, often in the form of nitrates. In other places flood irrigation leaches alkalis and other salts past the root zone and is recognized as beneficial to raise the soils pH above and acidic level. Aquifer level as a quantitative measurement may not reflect quality. Greg
Yes to what Greg said. Also, it would be wrong (or at least burden-shifting) to take water from over-tapped surface water systems, just so we can try to fix the other problem of overdraft.